1. Technical Field
The present invention relates to a method for producing a rubber composition, and further relates to a rubber composition obtained by the method and a pneumatic tire.
2. Related Art
It is conventionally known in a rubber composition used in a tread rubber of a pneumatic tire to add a polymer gel containing a functional group in order to improve grip performance (wet grip performance) on a wet road surface. For example, JP-A-2011-046875 and EP2716700A1 propose that 10 to 150 parts by mass of silica and 10 to 30 parts by mass of a hydroxyl group-containing diene rubber gel having a glass transition temperature of −40 to −10° C. are added to 100 parts by mass of a rubber component.
On the other hand, in the case of using silica as a filler in a rubber composition for a tread, it is known to use a modified diene rubber having a functional group introduced therein which has an interaction with silica for the purpose of improving rolling resistance performance and wet grip performance by the improvement of dispersibility of silica (for example, see US2012/0214903A1).
Thus, a polymer gel having a functional group is used to improve wet grip performance. However, where the polymer gel is used together with a modified diene rubber that improves dispersibility of silica, it is the actual situation that the effect is not always sufficient and does not reach the level expected in the wet pip performance.